The present invention relates to an optical angle characteristic measuring apparatus capable of measuring, as a function of the angle, the intensity of light emitted from a sample.
By irradiating light to a sample and measuring the emitted light for its angle dependency and changes with the passage of time, there can be obtained information of the particles as to sizes, shapes, molecular weights, thermal agitation and the like.
Apparatus for measuring the angle dependency of emitted light is called an optical angle characteristic measuring apparatus. More precisely, apparatus for measuring the angle dependency of scattered light is called a light scattering intensity measuring apparatus. The light scattering intensity measuring apparatus is arranged such that light is irradiated in one direction to a sample, that a detector for detecting the scattered light is disposed on a goniometer rotatable around the sample, and that the scattered light is detected at a variety of angles with the goniometer rotated.
However, when it is intended to measure such scattered light in a wide range of angle with the light scattering intensity measuring apparatus, it takes several tens of minutes or more for measurement. This is disadvantageous in time efficiency. Further, measurement cannot disadvantageously be conducted on a sample which undergoes, within the measuring period of time, changes with the passage of time such as association, cohesion or the like.
For shortening the measuring period of time, it is required to reduce the number of measuring angle points. This sacrifices the data precision.
Further, to prevent the observation point from deviating when the goniometer is rotated, it is required to design apparatus with very high precision. This disadvantageously requires much labor.
In this connection, there is developed apparatus for detecting the scattered light with a plurality of detector fixed in an annular manner around the sample. In this apparatus, however, the number of measuring angles is limited to a certain value.
It is an object of the present invention to provide an optical angle characteristic measuring apparatus for measuring, as a function of the light emitting angle, the intensity of light emitted from a sample, which apparatus is capable of detecting, in a very short period of time, the emitted light in a wide range of angle up to 360xc2x0.
(1) According to the present invention, an optical angle characteristic measuring apparatus comprises: a ellipsoidal mirror for reflecting and condensing the emitted light from a sample disposed in the vicinity of the first focal point of the ellipsoidal mirror; image-forming means disposed in the vicinity of the second focal point of the light reflected from said ellipsoidal mirror for forming, on a record face, the image formed on the surface of the ellipsoidal mirror; and record means for recording the image formed by the image-forming means.
According to the arrangement above-mentioned, the image-forming means can form, on a record face, the image formed on the mirror face of the ellipsoidal mirror. Accordingly, the record means can record the intensity pattern of the emitted light.
Thus, the apparatus according to the present invention is different in provision of the image-forming means and the record means from the inventions disclosed in Japanese Patent Laid-Open Publications No. H2-223845 and S64-29737 in each of which a reflection mirror is utilized merely as a kind of an integrating sphere.
According to the optical angle characteristic measuring apparatus of the present invention, the angle dependency data of emitted light can simultaneously be measured in a very wide angle range without the optical system component elements moved. This remarkably improves the measurement in time efficiency. Accordingly, the apparatus of the present invention can measure a sample, undergoing a change with the passage of time, which has conventionally been measured with difficulty. For example, dynamic scattering characteristics can also be measured.
Further, the apparatus of the present invention has no movable members as optical system component elements. This not only improves the measurement in stability and reliability, but also lengthens the lifetime of the apparatus. The number of the optical system component elements is reduced. This is advantageous in view of cost and production efficiency.
Further, according to the arrangement of the present invention, the image formed on the mirror face of the ellipsoidal mirror can be formed on the record face in a stigmatic manner.
The following description will discuss the operation of this optical angle characteristic measuring apparatus with reference to FIG. 1 illustrating a specific arrangement of the present invention.
A sample 23 is disposed in the vicinity of a first focal point of an ellipsoidal mirror 24. Light emitted from the sample 23 is reflected and condensed by the ellipsoidal mirror 24 and then incident upon a camera 26 serving as record means through an image-forming lens 25 disposed at a second focal point of the ellipsoidal mirror 24.
The image formed on the recording face of the camera 26 represents the image formed on the mirror face of the ellipsoidal mirror 24, and corresponds to the emitting angle at which light is emitted from the sample. It is a remarkable feature that because of the nature of an ellipsoidal mirror, this image is an image formed in a stigmatic manner.
FIG. 2 is a view of coordinates illustrating the light emitting angle. As shown in FIG. 2, a plane sample 23 is assumed and the original point is located in a position which serves as the point to be measured on the sample 23. As shown in FIG. 2, there is formed a system of orthogonal coordinates x, y, z in which an angle xcex8 is formed between the light direction and the y-axis and an angle xc3x8 is formed between the light image projected on the x-z plane and the x-axis. These angles xcex8 and xc3x8 are called visual field angles. A position on the mirror face of the ellipsoidal mirror 24 can be identified by these visual field angles xcex8 and xc3x8.
FIG. 3 is a projection view of the angles xcex8, xc3x8 reflected on the mirror face of the ellipsoidal mirror 24. The real image of this projection view is formed on the recording face of the camera 26 by the operation of the image-forming lens 25.
It is therefore possible to measure the optical characteristics of the sample, according to the visual field angles, such as polarization characteristics, scattering angle characteristics, reflectivity data, transmissivity data, luminance data, chromaticity data and the like. Further, the range of the visual field angles is stigmatic and extends widely from 0xc2x0 to 90xc2x0 for xcex8 and from xe2x88x9220xc2x0 (340xc2x0) to 200xc2x0 for xc3x8 as shown in FIG. 3.
It can be considered that the curvature of the ellipsoidal mirror 24 deviates from the ideal one. In this case, the projection view in FIG. 3 becomes different from the calculated distribution. It is therefore required to correct the distribution with the use of a standard sample (for example, a transmission-type grating) of which visual field angles are known.
(2) The ellipsoidal mirror may be replaced by a spherical mirror formed from a portion of a spherical surface or a conical mirror formed from a portion of a conical surface. In such a case, too, the projection view is different from the calculated distribution. It is therefore required to correct the distribution with the use of a standard sample (for example, a transmission-type grating) of which visual field angles are known. The best advantage of the arrangement above-mentioned is that such spherical or conical mirror can more readily be produced as compared with the ellipsoidal mirror.